Since I already used Parallels with the Bootcamp-Partition before the Upgrade to Monterey plus the fact that I actually already have a working Bootcamp-Partition, I should normally not need any additional space or files, at least that's what I thought. For either solution, you can buy a license for Windows 10 online at Microsoft, Amazon or your favorite software retailer, and download the file needed to install Windows. If cost is a factor, then you should certainly consider using Boot Camp. Another thing that seemed not ok to me was that before I could go to select the „Source-File' I got the information that about 17GB of my disc-space would be needed. Boot Camp comes free with your Mac, while Parallels will cost you 80 and up per year. When I simply tried to select the entire Bootcamp-Disc-Partition I could not continue. The problem with this was, that at the last step I did not know which file to choose as the „Source-File' for the installation. However, the advantage of Boot Camp is that it’s free to use on Intel Macs including those running Catalina, Big Sur, Monterey and Ventura. To switch between the two, you need to shut down and restart your Mac. However I found a small guide to connect a Bootcamp-Partition to Parallels without choosing the mentioned option on the Installation Assistant: Boot Camp is different because it only allows you to boot your Mac in either macOS or Windows. This issue with Monterey and Intel-based Macs is already documented and there is no (official) workaround listed. After upgrading to macOS Monterey and starting Parallels 16.5 I was not able to use/connect my - already installed and with previous macOS-versions used - Bootcamp-Partition because the Parallels Installation Assistant did not show the option „Use Windows from Boot Camp' like it traditionally did.

Bootcamp vs parallels reddit